Measurement uncertainty evaluation of the Total Antioxidant Capacityof human plasma tested by the CUPRAC-BCS method

This paper deals with the evaluation of the measurement uncertainty of Total Antioxidant Capacity (TAC) of human plasma estimated by the CUPRAC-BCS method, a photometric method that uses the redox couple Cu(II)/Cu(I) to estimate the reducing capacity of a fluid. The urate is usually used as reference molecule in the clinical chemistry field. In this work, the measurement uncertainty was assessed on TAC values obtained using both urate and Cu(I), as reference species, and two measurement apparatuses i.e. i) a UV-visible spectrophotometer and ii) a routine auto-analyser. A comprehensive list of relevant sources of uncertainty was compiled. Uncertainties estimated are related to the effects of: calibration curve, repeatability, temperature, pH, concentration of the reference stock solutions, electronic exchange of the redox reaction between Cu(II) and urate. The measurements performed with the automatic apparatus associated with the use of Cu(I) ion for the calibration provide the lowest uncertainty, u(TAC)/TAC = 0.0094.